scholarly journals Comparison of Surface Tension Models for the Volume of Fluid Method

Processes ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 542 ◽  
Author(s):  
Kurian J. Vachaparambil ◽  
Kristian Etienne Einarsrud
Keyword(s):  
Surface Tension ◽  
Multiphase Flow ◽  
Capillary Rise ◽  
Surface Tension Force ◽  
Surface Force ◽  
Parallel Plates ◽  
Time Step ◽  
Mesh Resolution ◽  
Active Research ◽  
Spurious Currents

With the increasing use of Computational Fluid Dynamics to investigate multiphase flow scenarios, modelling surface tension effects has been a topic of active research. A well known associated problem is the generation of spurious velocities (or currents), arising due to inaccuracies in calculations of the surface tension force. These spurious currents cause nonphysical flows which can adversely affect the predictive capability of these simulations. In this paper, we implement the Continuum Surface Force (CSF), Smoothed CSF and Sharp Surface Force (SSF) models in OpenFOAM. The models were validated for various multiphase flow scenarios for Capillary numbers of 10 − 3 –10. All the surface tension models provide reasonable agreement with benchmarking data for rising bubble simulations. Both CSF and SSF models successfully predicted the capillary rise between two parallel plates, but Smoothed CSF could not provide reliable results. The evolution of spurious current were studied for millimetre-sized stationary bubbles. The results shows that SSF and CSF models generate the least and most spurious currents, respectively. We also show that maximum time step, mesh resolution and the under-relaxation factor used in the simulations affect the magnitude of spurious currents.

A Numerical Method for Capillarity-Driven Free Surface Flows

2005 ◽  
Author(s):  
Albert Y. Tong ◽  
Zhaoyuan Wang
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Level Set ◽  
Surface Tension Force ◽  
Surface Force ◽  
Volume Of Fluid ◽  
Free Surface Flows ◽  
Tension Force ◽  
Navier Stokes Equation ◽  
Spurious Currents

The continuum surface force (CSF) method has been extensively employed in the volume-of-fluid (VOF), level set (LS) and front tracking methods to model surface tension force. It is a robust method requiring relatively easy implementation. However, it is known to generate spurious currents near the interface that may lead to disastrous interface instabilities and failures of grid convergence. A different surface tension implementation algorithm, referred to as the pressure boundary method (PBM), is introduced in this study. The surface tension force is incorporated into the Navier-Stokes equation via a capillary pressure gradient while the free surface is tracked by a coupled level set and volume-of-fluid (CLSVOF) method. It has been shown that the spurious currents are greatly reduced by the present method with the sharp pressure boundary condition preserved. The numerical results of several cases have been compared with data reported in the literature and are found to be in a close agreement.

scholarly journals On sharp surface force model: Effect of sharpening coefficient

2020 ◽  
Vol 3 (3) ◽  
pp. 226-232 ◽  
Author(s):  
Kurian J. Vachaparambil ◽  
Kristian Etienne Einarsrud
Keyword(s):  
Surface Tension ◽  
Capillary Rise ◽  
Surface Tension Force ◽  
Surface Force ◽  
Volume Of Fluid ◽  
Tension Force ◽  
Force Model ◽  
Relative Ease

Abstract Amongst the multitude of approaches available in literature to reduce spurious velocities in Volume of Fluid approach, the Sharp Surface Force (SSF) model is increasingly being used due to its relative ease to implement. The SSF approach relies on a user-defined parameter, the sharpening coefficient, which determines the extent of the smeared nature of interface used to determine the surface tension force. In this paper, we use the SSF model implemented in OpenFOAM® to investigate the effect of this sharpening coefficient on spurious velocities and accuracy of dynamic, i.e., capillary rise, and static bubble simulations. Results show that increasing the sharpening coefficient generally reduces the spurious velocities in both static and dynamic cases. Although static millimeter sized bubbles were simulated with the whole range of sharpening coefficients, sub-millimeter sized bubbles show nonphysical behavior for values larger than 0.3. The accuracy of the capillary rise simulations has been observed to change non-linearly with the sharpening coefficient. This work illustrates the importance of using an optimized value of the sharpening coefficient with respect to spurious velocities and accuracy of the simulation.

scholarly journals Relaxation and breakup of a cylindrical liquid column

1970 ◽  
Vol 39 (2) ◽  
pp. 57-64 ◽  
Author(s):  
Mohammad Ali ◽  
Akira Umemura
Keyword(s):  
Surface Tension ◽  
Stokes Equations ◽  
Capillary Wave ◽  
Three Dimensional ◽  
Surface Tension Force ◽  
Surface Force ◽  
Computer Code ◽  
Vof Method ◽  
Liquid Column ◽  
Navier Stokes

Instability of capillary wave and breakup of a square cylindrical liquid column during its relaxation have been investigated numerically by simulating three-dimensional Navier-Stokes equations. For this investigation a computer code based on volume-of-fluid (VOF) method has been developed and validated with published experimental results. The result shows that the agreement of numerical simulation is quite well with the experimental data. The code is then used to study the capillary wave and breakup phenomena of the liquid column. The investigation shows the underlying physics during relaxation of the square cylindrical liquid column, illustrates the formation and propagation of capillary wave, and breakup processes. The breakup behavior for the present configuration of the liquid column shows some significant differences from those predicted by conventional jet atomization theories. The formation of capillary wave is initiated by the surface tension on the sharp edge of the square end of the cylinder and the propagation of the wave occurs due to the effect of surface tension force on the motion of the fluid. The propagation of capillary wave to the end of liquid column causes a disturbance in the system and makes the waves unstable which initiates the breakup of the liquid column. The characteristics of the capillary wave show that the amplitude of the swell grows faster than the neck of the wave and that of the tip wave grows much faster than the other waves. The velocity of the liquid particle is dominated by the pressure in the liquid column. Keywords: Instability; Continuum surface force; Liquid disintegration; Capillary wave; Surface tension; VOF method doi:10.3329/jme.v39i2.1847 Journal of Mechanical Engineering, Vol. ME39, No. 2, Dec. 2008 57-64

Numerical Study on Impingement of a Droplet upon a Liquid Film

2010 ◽  
Vol 44-47 ◽  
pp. 2499-2503
Author(s):  
Hong Liu ◽  
Mao Zhao Xie ◽  
Su Chun Wang ◽  
Ming Jia
Keyword(s):  
Surface Tension ◽  
Liquid Film ◽  
Stokes Equations ◽  
Numerical Study ◽  
Surface Tension Force ◽  
Surface Force ◽  
Navier Stokes ◽  
Initial Kinetic Energy ◽  
Droplet Impingement ◽  
Fine Grid

This paper reports progress in the numerical simulations of a droplet impingement upon the wall film of the same liquid. The full Navier-Stokes equations are solved in axisymmetric formulation. The surface tension force is modeled by a continuum surface force (CSF) model. An adapting local refinement technique is used to provide the fine grid coupled by the volume-of fluid (VOF) method for tracking the interface between the gas and the droplet and liquid film. Results indicate that the motion behavior of droplet impingement upon the liquid film is dominantly influenced by the initial kinetic energy and the thickness of the film as well as the surface tension and the liquid viscosity.

On methods to reduce spurious currents within VOF solver frameworks. Part 1: a review of the static bubble/droplet

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Venkatesh Inguva ◽  
Andreas Schulz ◽  
Eugeny Y. Kenig
Keyword(s):  
Surface Tension ◽  
Aqueous Phase ◽  
Level Set ◽  
Capillary Number ◽  
Classical Case ◽  
Surface Tension Force ◽  
Artificial Viscosity ◽  
Special Treatment ◽  
Two Phase ◽  
Spurious Currents

AbstractIn two-phase flows in which the Capillary number is low, errors in the computation of the surface tension force at the interface cause Front-Capturing methods such as Volume of Fluid (VOF) and Level-Set (LS) to develop interfacial spurious currents. To better solve low Capillary number flows, special treatment is required to reduce such spurious currents. Smoothing the phase indicator field to more accurately compute the curvature or adding interfacial artificial viscosity are techniques that can treat this problem. This study explores OpenFOAM, Fluent and StarCCM+ VOF solvers for the classical case of a static bubble/droplet immersed in a continuous aqueous phase, with the focus on the ability of these solvers to adequately reduce spurious currents. The results are expected to be helpful for practicing chemical engineers who use multiphase CFD solvers in their work.

New Implementations of Surface Tension Forces for PLIC-VOF Methods

2010 ◽  
Author(s):  
Jesu´s Castro ◽  
Assensi Oliva ◽  
Eduardo Garci´a-Rivera
Keyword(s):  
Surface Tension ◽  
Surface Tension Force ◽  
Surface Force ◽  
Polar Coordinates ◽  
Staggered Grid ◽  
Reconstruction Algorithms ◽  
Interface Location ◽  
Parasitic Currents ◽  
Force Calculation ◽  
Surface Tension Forces

A comparative study has been carried out between different models of implementing surface tension for PLIC-VOF methods: i) the well known Continuum Surface Force (CSF); ii) Staggered Grid Interface Pressure (SGIP); iii) Modified Meier’s. As main difference with respect the CSF model, the two last use information of the interface location for the calculation of the surface tension forces, therefore, they need a model of interface reconstruction. The models will be tested under static and dynamic conditions, for the case of a drop and bubble between water and air. In order to reduce the ‘parasitic’ currents that is characteristic of this type of models, two different strategies are used: i) a new method for the calculation of the interface curvature based on the use of polar coordinates; ii) the use of kernels for smoothing the jump of the colour function and the interface. Additionally, the influence of the order of accuracy of the reconstruction algorithms employed that affect the curvature estimation and the surface tension force calculation is also checked. After testing the different cases, it can be concluded that SGIP and modified Meier perform in a comparable way, and much better than CSF model without kernel, that is only competitive with the use of the kernels. However, modified Meier is preferred respect SGIP due to its straitghforward implementation on unstructured meshes.

Numerical Analysis of Heat Transfer of a Flow Confined by Wire Screen in Lithium Bromide Absorption Process

2014 ◽  
Vol 348 ◽  
pp. 40-50 ◽  
Author(s):  
Herbert Obame Mve ◽  
Romuald Rullière ◽  
Rémi Goulet ◽  
Phillippe Haberschill
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Numerical Analysis ◽  
Lithium Bromide ◽  
Surface Tension Force ◽  
Surface Force ◽  
Geometrical Parameters ◽  
Force Model ◽  
Vof Model ◽  
Static Contact

The present study deals with the numerical analysis of heat transfer inside a lithium bromide solution flowing down between finely meshed plastic wire screens. These screens confine the flow through capillary action while allowing the water vapor transfer inside an innovative absorber technology. The complex menisci shape formed on the confinement grid level, where the surface tension forces are of first importance, are reconstructed by a volume of fluid (VOF) model. A continuum surface force model is used to account for the surface tension force. A static contact angle is used to define the wall adhesion. A new algorithm, consisting to set an unique constant temperature at the liquid/vapour interface and to determine the evolution of heat transfer characteristics over the simulation domain, has been implemented and validated by analytical solutions. A parametric study has been conducted to determine the effect of the inlet velocity and the geometrical parameters (wire diameter and the number of divisions).

scholarly journals Coalescence Prevention Algorithm for Level Set Method

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Matthew L. Talley ◽  
Matthew D. Zimmer ◽  
Igor A. Bolotnov
Keyword(s):  
Surface Tension ◽  
Liquid Film ◽  
Level Set ◽  
Computational Cost ◽  
Surface Tension Force ◽  
Bubble Coalescence ◽  
Film Drainage ◽  
Drainage Time ◽  
Computational Mesh ◽  
Mesh Resolution

An algorithm to prevent or delay bubble coalescence for the level set (LS) method is presented. This novel algorithm uses the LS method field to detect when bubbles are in close proximity, indicating a potential coalescence event, and applies a repellent force to simulate the unresolved liquid drainage force. The model is introduced by locally modifying the surface tension force near the liquid film drainage area. The algorithm can also simulate the liquid drainage time of the thin film by controlling the length of time the increased surface tension has been applied. Thus, a new method of modeling bubble coalescence has been developed. Several test cases were designed to demonstrate the capabilities of the algorithm. The simulations, including a mesh study, confirmed the abilities to identify and prevent coalescence as well as implement the time tracking portion, with an additional 10–25% computational cost. Ongoing tests aim to verify the algorithm's functionality for simulations with different flow conditions, a ranging number of bubbles, and both structured and unstructured computational mesh types. Specifically, a bubble rising toward a free surface provides a test of performance and demonstrates the ability to consistently prevent coalescence. In addition, a two bubble case and a seven bubble case provide a more complex demonstration of how the algorithm performs for larger simulations. These cases are compared to much more expensive simulations capable of resolving the liquid film drainage (through very high local mesh resolution) to investigate how the algorithm replicates the liquid film drainage process.

Sign in / Sign up

Export Citation Format

Share Document